Metal in the Microwave! Who would have thunk it?

We all remember the movie Under Seige, when that whirling dervish, Steven Segal, scrunched up some  cooking foil, chucked it in the oven, slammed the door and pressed go.  Thereby fashioning an improvised bomb to blast all the bad guys.  Turns out Stephan was playing a little loose with the facts.  Aluminium is a very stable metal and cannot explode. It also makes up most of the Microwave Oven cavity

Here’s the Science

Microwaves are reflected by metal but can build up a localised charge which can discharge to an adjacent metal with an opposite charge – thereby causing a little spark.  Smooth, round pieces of metal will not concentrate the charge and are safe to use in a microwave environment.  The walls of the oven are made of Aluminium!  All modern ovens now use anodised aluminium which further protects the walls from electrical discharge.  The anodised layer acts as an insulator and any arc will be very weak and will only stain the surface.

This is handy as it allows us to develop hot metal plates to brown and sear some tasty foods.